1. Field of the Invention
The present invention concerns a contactless position and displacement measuring device including at least one light source and at least one photosensor adapted to move relative to each other. When illuminated by a light beam emitted by the light source the photosensor generates at least one electrical signal representative of the position of the source relative to the photosensor.
2. Description of the Prior Art
In some prior art devices for measuring position and displacement the position of a mobile object is marked by a cursor that moves along a resistive or potentiometer track. A first drawback of this type of sensor is a result of their lack of precision because of the wear caused by the cursor rubbing on the resistive or potentiometer track which reduces the service life of the sensor. This makes these devices unsuited to applications in which the position of the mobile object must be defined with great precision. Furthermore, the service life of such devices is further limited if they operate in severe environments, in particular when there are high temperatures and high levels of vibration.
Other prior art devices include contactless position sensors known as continuous lateral effect sensors. Such sensors generally comprise a photosensitive cell including a PIN junction which when illuminated by a light spot generates an electrical charge proportional to the luminous intensity of said spot. The electrical charge generated moves across the P area of the PIN junction. Given that said P area has a uniform resistivity, the photocurrent collected by an end electrode is inversely proportional to the distance between the position of the light spot and the electrode concerned.
One drawback of this type of sensor is the result of the fact that the photosensitive cells are not perfectly linear, in particular because the surface resistance of the P area of the PIN junction is not homogeneous. Moreover, the electrical charge that moves across the P area depends on the temperature and on the luminous intensity as well as on the physical characteristics of the PIN junction.
The aim of the invention is to provide a contactless position and displacement measuring device adapted to deliver electrical signals independent of temperature, of variations in the luminous intensity delivered by the source and of the physical characteristics of the photosensitive cell used to generate said electrical signals.
Another aim of the invention is to provide a contactless position and displacement measuring device including a photosensor the dimensions and the shape of which can easily be adapted to detect and to measure the displacements of an object on a rectilinear trajectory or on a curvilinear trajectory.